Silicone compositions find use in a wide variety of applications since their cured products have excellent characteristics including weathering, heat resistance and transparency as well as hardness, elongation and other rubber properties. In particular, silicone resins due to their heat resistance and UV resistance are now in widespread use as encapsulants for optoelectronic devices such as blue or white high-intensity LEDs. However, prior art silicone resins have so high a coefficient of thermal expansion and a gas permeability that they often crack upon thermal cycling, causing disconnection and other troubles. In addition, corrosive gases can penetrate through the encapsulating silicone resin to cause corrosion to the silver surface of a reflector of LED, undesirably resulting in a reduced luminance.
Patent references relating to the present invention include WO 2003/093393 (JP-A 2005-524737), JP-A 2004-179644, and JP-A 10-284759.